1. Field of the Invention
The present invention relates to an organic integrated device for thin film transistor and light emitting diode, and more particularly to an organic integrated device including top-gate thin film transistor and light emitting diode.
2. Description of the Prior Art
Organic light emitting diode (OLED) is a LED that uses an organic layer as the active layer. In recent years, OLED has been gradually applied in flat panel displays and has many advantages, such as operating at low voltage, high brightness, light weight and slim, full viewing angle, and high effective contrast ratio.
Organic thin film transistor (OTFT) is a TFT that uses an organic layer to serve as the active layer and has been used to drive OLED. In recent years, in order to simplify the process and decrease the production cost, some researchers have developed integration technology that fabricates OLED and OTFT monolithically (i.e., on the same substrate).
For example, Sirringhaus et al. in University of Cambridge disclose an integrated device of OLED and bottom-gate OTFT, which uses MEH-PPV [poly[2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylene-vinylene]] as the light emitting layer of OLED. Since the OLED irradiates through an opaque metal electrode, the light efficiency is poor. Also, the production process is complicated (Science, Vol. 280, p.1741).
Choi et al. in U.S. Pat. No. 5,970,318 disclose another integrated device of OLED and bottom-gate OTFT. In the OTFT, the organic semiconducting layer is organic charge transfer complex or thiophene polymer, and the dielectric layer is also organic material. However, it is very difficult to pattern such organic material, making the OTFT fabrication difficult.
Nagami in U.S. Pat. No. 6,037,718 discloses an integrated device of an OLED and an npn-type transistor stacked on the OLED to drive the OLED. However, many layers of organic material are stacked, which makes the process complicated.
Bao et al. in U.S. Pat. No. 6,150,668 disclose another integrated device of OLED and bottom-gate OTFT. An organic semiconducting material is used as both the semiconducting layer of the OTFT and the hole transport layer of the OLED. However, after the organic semiconducting material is deposited, there is a need to form an additional protection layer in order to increase device reliability. In addition, since the organic semiconducting layer is not patterned, it is probable that current leakage or crosstalk between pixel and pixel occurs, making it difficult to meet the circuit design requirements.